The present invention relates to metallic strip plating apparatus in general and in particular to apparatus for continuously plating metal on a metal strip having a plurality of stationary fluid jets and a pair of split concentric annular rotatable members for continuously transporting a metal strip past the jets.
Plating apparatus of the type relating to the present invention is used for plating lead frames used by the semiconductor industry in the fabrication of integrated circuits and the like. Typically, a strip to be plated comes in a large coil. The strip is unwound from the coil and fed through a plating apparatus and plated with one or several different types of metals. When a plurality of metals are plated on a single strip, a separate plating apparatus is provided for each metal. Typically, the apparatus thus provided is placed side by side and in series relative to the strip.
Initially, when any part of a strip is required to be plated, the entire surface of the strip, or at least the entire surface on one side of a strip was plated. When one or both sides of a strip are plated in their entirety, a great deal of material is required. Since only a portion of a strip is frequently all that is required to be plated, there is waste and needless cost both in terms of money and in materials.
Another form of strip plating apparatus which is also in use is called a step selective plating apparatus. In apparatus of this type, there is provided a plurality of stationary fluid jets positioned along a line between a pair of rails or side walls. A strip to be plated is introduced into one end of the apparatus, passes over the jets and exits from the opposite end. The strip is introduced in a step fashion. The strip is moved a predetermined distance over the jets while the jets are turned off. The jets are then turned on and the strip is plated. After a predetermined time the jets are once again turned off and the apparatus replenished with a fresh unplated length of strip.
It will be appreciated that the "step" type apparatus tends to be slow, and possibly even more importantly, if any of the jets is clogged, a non-uniform plating will result.
Still another type of selective strip plating apparatus is provided with a rotatable wheel-like assembly. In the interior of the wheel assembly is a fluid manifold. Coupled to the fluid manifold is a plurality of fluid jets or simply a fluid outlet, for dispensing plating fluid through a slot in the periphery of the wheel assembly and against a strip transported thereon. As the wheel-like assembly is rotated carrying the strip on its periphery, the fluid jets or other fluid outlets also rotate therewith since they typically constitute an integral part thereof.
Unlike the "step" type apparatus described above, the rotatable wheel and fluid jet assembly is considered a high-speed plating apparatus; however, like the "step" type apparatus, if any of the jets or other fluid outlets becomes clogged, a non-uniform plating will result. This is due to the fact that in both types of plating apparatus, a single jet or outlet, and none other, is associated with a single section of strip.